Patent GB-816679-A (GB)
Title: Improvements in or relating to coated paper and methods of manufacturing the same
IPC: C09J189/00
Filed: 1955-10-27
Abstract: A paint comprises an aqueous composition containing finely-divided pigment or filler, and a dispersed proteinaceous adhesive coagulable by free multivalent metal ions having a positive valence of 3 or more, which are held in the aqueous composition in a captive unreactive condition in a dissolved complex formed as a reaction product of one or more multivalent metal ions, one or more anions of organic acids, and a basic reactant soluble in water to yield hydroxyl ions, the complex being substantially decomposed by removal of the hydroxyl ions from the dispersion so that the metal ions are liberated and coagulate the proteinaceous adhesive.  The complex which may be a chelate complex in which the organic acid is a hydroxycarboxylic acid and the basic reactant is ammonium hydroxide may be decomposed by evaporation of the aqueous phase at a temperature above 20 DEG  C.  The paint may be applied to paper, the exposed surface of which may be dried, for the purpose of coagulating the adhesive, in intimate contact with a highly-polished heated drum, as described in Specifications 331,578, [Class 96], and 714,723, [Group VIII], and separated therefrom when dry so that a cast coated surface is formed on the paper.  Specified proteinaceous adhesives are casein and soy protein.  Multivalent metal ions disclosed are aluminium, ferric, chromic, stannic, vanadyl, and zirconyl ions.  The organic acid anion may be derived from an open-chain aliphatic hydroxycarboxylic acid which may be mono-, di-, or poly-basic and may contain one or more hydroxyl groups, e.g. tartaric, citric, malic, lactic, glycolic or hydracrylic acid, aromatic, e.g. salicylic acid, or any cyclic, organic acid, or their carboxylates.  The basic reactant may be a substituted or unsubstituted ammonium hydroxide, an alkanolamine, or a primary, secondary or tertiary amine, e.g. morpholine.  The composition, which may have a pH of 9 to 12, contains pigments, e.g. titanium dioxide, calcium carbonate, and may contain alkaline stabilizers, e.g. tetrasodium pyrophosphate, clays, styrene-butadiene copolymers, silicone foam reducing agents, and viscosity reducing agents, e.g. dicyandiamide.ALSO:An aqueous protein composition comprises a dispersed proteinaceous adhesive coagulable by free multivalent metal ions having a positive valence of 3 or more, which are held in the aqueous composition in a captive unreactive condition in a dissolved complex formed as a reaction product of one or more multivalent metal ions, one or more anions of organic acids, and a basic reactant soluble in water to yield hydroxyl ions, the complex being substantially decomposed by removal of the hydroxyl ions from the dispersion so that the metal ions are liberated and coagulate the proteinaceous adhesive.  The complex which may be a chelate complex in which the organic acid is a hydroxycarboxylic acid and the basic reactant is ammonium hydroxide may be decomposed by evaporation of the aqueous phase at a temperature above 20 DEG  C.  Specified proteinaceous adhesives are casein and soy protein.  Multivalent metal ions disclosed are aluminium, ferric, chromic, stannic, vanadyl and zirconyl ions.  The organic acid anion may be derived from an open chain aliphatic hydroxycarboxylic acid which may be mono-, di- or poly-basic and may contain one or more hydroxyl groups, e.g. tartaric, citric, malic, lactic, glycolic or hydracrylic acid, aromatic, e.g. salicylic acid, or any cyclic organic acid, or their carboxylates. The basic reactant may be substituted or unsubstituted ammonium hydroxide (as ammonia water), an alkanolamine, or a primary, secondary or tertiary amine, e.g. morpholine.  The basic metal complex may be formed by adding an aqueous solution containing the multivalent metal ion, e.g. in the form of the metal salt such as the sulphate, chloride, acetate or nitrate, and the organic acid, or its carboxylate, e.g. sodium, potassium or calcium salts, or ester thereof, to an aqueous solution of the basic reactant. Specifications 331,578, [Class 96], and 714,723, [Group VIII], are referred to.